fossil molluscs from the miocene masuda group at …...fossil molluscs from the miocene masuda group...
TRANSCRIPT
Mem . 15, pp
Fac. Sci., Shimane Univ.
89-108 Dec. 20, 1981
Fossil Molluscs from the Miocene Masuda
Group at Okuda, Masuda City
Molluscan Fossils from Various Localities
in Shimane Prefecture, Part 2
Katsumi TAKAYASU Department of Geology, Faculty of Science, Shimane Unrversity
(Received September 5, 1981)
Introduction
Abundant fossils of Vicarya and other molluscs were found by the students of a
jounior high school at Okuda in the south of Masuda City in December of 1977
(Textfig. l). Recently the details were reported by TANAKA (1981). After this dis-
covery, many specrmens have been collected on the chance of the geological training
for students of Shimane University and some excursions at the site. Here to fore,
twenty species of molluscs have been identified by the author's examination of these
specimens and TANAKA'S collections. In this paper, they will be described
The author wishes to express.his hearty thanks to Mr. Ikutaro TANAKA of Kuraki
Junior High School, Muika-ichi-cho, Shimane Prefecture, for providing fossil specimens
Textfig.
l+ / *
H amada f'
~~:~;(~,/
Masuda _>-- ~ ,: .
~, jt -- ;~~~~~~'~:~:~ _ { ~
- '1~ T suw ano ¥/ ~ ~_/_ ;lA~;
l ¥t ¥ ~ - ! 5km ¥~._lJ ¥J
1 . Map showing the fossil locality.
'elwamryokota", I : 25,000 in scale)
(Taken from the topographical map
90 Katsunu TAKAYASU and Dr. JunJi ITOIGAWA of Nagoya University, Professor Masahiro OKUBO and Dr.
Takao TOKUOKA Of Shimane University for their helpful advice
Geologic Outline
The Miocene marine sediments distributed in Masuda City are named the Masuda
Group and is divided into a lower unit, the Toyoda Formation, and an upper unit,
the Yasuda Formation (FUJITA, 1964). The Toyoda Formation is about 1 10 meters
in thickness, and consists of conglomerates, sandstones and alternating beds of sand-
stone and shale. The Yasuda Formation exceeds 80 meters in thickness, and is re-
presented by black shale interbedded with sandstones and tuffs. Fourteen fossil
localities were shown in FUJITA (1964) and he listed 21 species of mollusca, 4 species
of plant, some crabs and fish scales. On the basis of such fossil molluscs as Batillaria
tateiwai, Cardium ogurai and Placopecten cf. nomurai, he regarded the Masuda Group
as the early Middle Miocene in age and correlated it with the Bihoku Group of the
Setouchi province.
The fossil locality of Okuda newly reported by TANAKA (1981) belongs to the lower
part of the Toyoda Formation. As shown in Textfig. 2, the strata of about 23 meters
thick at this locality consist mostly of dark colored sandy shales, but some beds of
breccra of the underlying Sangun metamorphic rocks are contained in the basal part
o
Textfig. 2. (~ieologic column_ of the fossil locality
LithicSection cha－racters Zonule
・ ■■● ■・
m・ 一 一一 一 一 一
（Weathered2◎・
一 一 一 一一 一 一 一
ZOne）■ ‘ ‘ ‘ 一
一 ・ ‘ 一 一 一 ■ 一 ‘ 一 一 一 一 一 一 一．
働 吋ε
O⑩ o
15一Salndy sha1e ～
ミ
1刺～何
’ 勺～
qCalcareous
刊
1
COnCretiOnS呵
q10・
．H
H藪麹 oS～mdy shaユe
）
o載
←”05tre∂”bed 附0∂rga
油養藻直召一丁∂亡e立waia
Sandy sha1e 一Cr∂ssOS亡カe∂5□
．乙雑1鎚 BrecCia口ψ S㎝dy sha1e
公．・．ぺ．． Breccia＆ss． 0ヱassoβ亡rea
鱗瀦蝸於ムSaハd．y sha1e
BreCCia∩ 口
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda City 91
Notes on the Molluscan Assemblage
The molluscan assemblage of this locality can be divided into three zonules which
are the C,rassostrea zonule, Vicarya-Tateiwaia-Crassostrea zonule and Cyclina-Anadara-
Macoma zonule in ascending order (Textfig. 2). The Crassostrea zonule is composed
exclusively of C. gravitesta which is swarmed in a few beds. The Vicarya-Tateiwaia-
Crassostrea zonule is composed mainly of Vicarya japonica, Tateiwaia tateiwai and
Crassostrea gravitesta with minor amount of Tateiwaia yamanarii. Vicarya and Tateiwaia are swarmed in a bed of about I .5 meters thick. Bivalves except Cl'assostrea
are scarcely found in this zonule. The Cyclina-Anadara-Macoma zonule is represented
by Cyclina? hwabongriensis, Anadara (Hataiarca) daitokudoensis and Macoma (Maconla)
izurensis, and contains other various species of mollusca. In this zonule, Crassostrea
does not swarm but is contained sporadically, and Vicarya is hardly found
The upward sequence of the representative molluscs mentioned above indicates
the environmental change from the brackish embayment to the coastal water area near
the bay-mouth.
Systematic Description
Class GASTROPODA
Order ARCHAEOGASTROPODA Family TROCHIDAE
Subfamily CALLIOSTOMlNAE Genus Tristichotrochus IKEBE 1 942
Tristichotrochus sp.
(Pl. I, fig. 10)_
Description : Shell small trochiform. Post nucleous whorls five in number. Ex-
ternal surface of the body whorl sculptured with fine, slightly beaded spiral threads
Shell base flat and with about 10 spiral grooves, Umbilicus closed
Dimensions :
DGSU* coll. cat. no.
T1800 Height (mm) Diameter (mm)
16.5+ 20.4
Remarks : The spire is crushed axially, and owing to the poor preservation, the
surface sculpture is not clear. This specimen somewhat resembles Tristichotrochus
* Abbreviation for Department of Geology, Faculty of Sclence Shimane Unrversrty Matsue
92 Katsunu TAKAYASU takeharai ITOIGAWA and SHIBATA (1976) from the Miocene Mizunami Group in outline
but differs from the latter i.n its large and rather solid shell
Order MESOGASTROPODA Family POTAMIDIDAE
Genus Tateiwaia MAKIYAMA, 1936
Tateiwaia tateiwai (MAKIYAMA, 1 926)
(P1. I, figs. 6, 7)
Batillaria tateiwai MAKIYAMA, 1926, pp. 147-148, P1. 12, figs. 5, 6; OTUKA, 1934, p. 624, Pl. 49,
fig. 71 ; NoMURA, 1935, p. 228, P1. 17, figs. 30-33.
Cerithium sakawotoi YOKOYAMA, 1929, p. 367, Pl. 25, fig. 4.
Tateiwaia tateiwai (MAKIYAMA), TAGUCHI, ONo and OKAMOTO, 1979, Pl. 3, figs. 24-26.
Description : Shell reratively small, turreted. Each whorl sculptured with about 12
axial ribs and 3 primary spiral threads ; the uppermost thread makes a row of shoulder
spines crossing the ax. ial ribs
Dimensions :
DGSU coll. cat. no.
Tl 709
T1710 T1711 T1712
Height (mm) 20.2 +
22.0
25.3
22.7
Max. diameter (mm) Pleural angle 8.5
7.6
9.4
7.8
ca. 100
90
lOo
90
Remarks: The species somewhat resembles Tateiwaia yamanarii (MAKIYAMA) in out-
line, but the foremer has characteristic shoulder spines and is smaller than the latter
Even if rt remains as the inner mould, the shoulder spines are obvious, therefore it is
clearly dlstinguishable from yamanarii.
Tateiwaia yamanarii (MAKIYAMA, 1 926) (.Pl. I, figs. 8, 9)
Batillaria yamanarii MAKIYAMA, 1 926, pp. 148-149, P1. 12, fig. 4 ; OTUKA, 1934, p. 624, P1. 49, figs.
80, 81 ; NoMURA, 1935, p. 228, Pl. 17, figs. 27, 28 ; KANNo and Ogawa, 1964, Pl. 2, fig. 17; MlzuNO,
1964. P1. 1, figs. 1-3.
Cerithium proavitunl YOKOYAMA, 1 929, p. 366, Pl. 25, fig. 3.
Batillaria (Tateiwaia) yamana,'ii (MAKIYAMA), OKAMOTO and TERACHI, 1 974. Pl. 47, fig. 1 2.
Tateiwaia yamanarii (MAKIYAMA), ITOIGAWA, SHIBATA and NISHIMOTO 1 974. p. 1 34, Pl. 40, figs
23-24b ; ITOIGAWA and NISHIKAWA, 1976, Pl. 35, fig. 1 5 ; TAGUCHI, ONO and OKAMOTO, 1979, Pl. 3, figs. 27, 28.
Description : Shell moderately small, turreted. Each whorl sculptured with 8 to 9
axial ribs and 3 primary theads; intercalated secondary spiral threads appeared on
the penultimate and body whorls. Axial ribs rise to prominent tubercles on the
mtersection with the middle primary spiral threads
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda Crty 93
Dimensions :
DGSU coll cat. no. Height (mm) T1 707
T1708 T1799
ca. 34.3
ca. 31.5
'_5.0+
Max, diameter (mm) Pleural angle 12.2
10.8
ca. 10.0
11'
11'
ll'
Remarks : This species, unlike T. tateiwai, has no shoulder spines and its lateral
sinus of growth-line is shallower than that of the latter
Genus Vicarya D'ARCHIAC and HAIME, 1 854
Vicarya japonica YABE and HATAI, 1 938
(Pl. II, fig. 1)
Vicarya callosa JENKINs, TAKEYAMA, 1 933, pp. 137-140, Pl. 14, figs. IaH~, 2a-b, 3.
Vicarya callosa .japonica (SAGA, MS), YABE and HATAI, 1938, p. 156, Pl. 31, figs. 1'_, 1 3.
Vicarya callosa japonica YABE and HATAI, MASUDA, 1956, Pl. 26, figs. I a-b ; YAMANA, 1 966, p. 34,
Pl. l, figs. Ia-b ; OKAMOTO and TERACHI, 1974, P1. 47, fig. 1 1 .
Vicarya (Shoshiroia) callosa japonica YABE and HATAI, KAMADA, 1960, Pl. 30, figs. 2a-b, 7, 8, Pl. 3 1 ,
figs. 2a-b; HAYASAKA, 1969, p. 48, Pl. 3, figs. 7, 8.
Pfcarya japonica YABE and HATAI, ITOIGAWA and NISHIKAWA, 1 976, P1. 3 5, fig. I O ; TAGUCHI, ONO
and OKAMOTO, 1979, Pl. 4, figs. 1, 2.
Description : Shell large, turreted, with about 1 5 whorls presented. First seven or
eight preserved whorls ornamented with three spiral cords ; uppermost or subsutural
cord with a distinct row of beads and other cords with no remarkable structure. In
ninth or tenth whorl, beaded row on subsutural cord becoming a distinct granular
row, and the middle cord with weakly beaded structure. From about 12th whorl,
subsutural row of granule becoming rapidly a distinct row of spinose tubercles ; tu-
Textfig. 3 . Surface ornamentation of the Vicarya japonica
from the Masuda Group x I .
94 Katsumi TAKAYASU bercles eight to ten in number in each whorl, and several fine secondary threads running
on the tuberculous row of the last two or three whorls. Middle and lower primary
cords rather indistinct on the lower whorls. Growth-lines observable on the lower
whorls, sigmoidal, deeply incurved backwards at the interspace between middle and
lower primary spiral cords (Textfig. 3)
Dimensions :
DGStJ coll cat no I Height (mm) T1 704
T1 705
T1 706
91.4+ 88.5+ 83.6+
Max. diameter (mm) Pleural angle ca. 42.0
37.5
32.2
ca. 190
ca. 190
ca. 180
Remarks : TAKEYAMA (1933) divided the Japanese Vicarya into V. callosa and V
verneuili yokoyamai. The each typical specimen has been obtained from the Bihoku
Group in the western Setouchi province and from the Mizunami Group in the eastern
Setouchi province respectively. According to TAKEYAMA, the chief differences between
them are as follows ; in callosa, the number of tubercles on subsutural band is almost
constant in all whorls, but in verneuili, there is no tubercle in the young stage excepting
many fine knots on spiral cords and a part of knots grades into the spinose tubercles
in the adult stage. YABE and HATAI (1938) insisted that the Japanese callosa differs
from the typical form of ca!losa from Java in having obliquely produced tubercles,
and gave the Japanese callosa a new subspecific name, japonica. They also regarded
yokoyamai as a subspecies of callosa, and pointed out that yokoyamai is distinguished
from .faponica by having auxiliary row of delicate beads or knots. However, IKEBE
(1939) supported TAKEYAMA'S view that yokoyamai is not a subspecies of callosa,
because the former differs from the latter not only in the sculptures on the young whorls
but also in the number of primary spiral cords below the subsutural band ; three in
yokoyamai and two in japonica.
The present specimen from the Masuda Group, in the young stage, somewhat
resembles yokoyamai in having beaded row on the subsutural cord and later on the
middle cord. However, in the adult stage of present specimen, the spiral cords below
the subsutural band are two in number and their beaded structure is not so remarkable
In addition, the subsutural spinose tubercles with several secondary spiral threads
are rather short and blunt in shape. These characteristics shown in the adult stage
are exactly those of V. japonica.
Family NATICIDAE
Genus Euspira AGASSlz, 1 839
Euspira meisensis (MAKIYAMA, 1 926)
(Pl. I, figs. 2, 3)
Polauces (Eusplra) mersensls MAKIYAMA 1926, pp. 150-151, P1. 12, fig. 7; MASUDA, 1956, P1. 26,
Fossil Molluscs from the Miocene Masuda Group at Okuda Masuda City 95
figs. 8a-b.
.Polinices meisensis MAKIYAMA, MASUDA, 1 967, Pl. I , figs. 24a-b.
Natica (Euspira) aff. meisensis (MAKIYAMA), OTUKA, 1938, p. 37, Pl. 3, figs. 25, 28.
Euspira meisensis (MAKIYAMA), SruKAMA, 1954, Pl. 7, figs. 2a-3b; ITOIGAWA, 1956, Pl. 3, fig. 10;
ARAKI, 1960, p. 109, P1. 9, figs. 1la-14; KAMADA, 1962, p. 158, Pl. 18, fig. 23 ; SAITo, 1962, Pl. 14,
figs. 23-25 ; HAYASHI and MlURA, 1973, Pl. 2, fig. 23 ; HAYASHI, 1973, Pl. 4, figs 6, 7 ; ITOIGAWA,
SHIBATA and NISHIMOTO, 1 974, p. 1 48, Pl. 45, figs. 1 3a-b, 1 8-19b ; ITOIGAWA and NrsrnKAWA,
1976, Pl. 35, fig. 1 7 ; TAGUCHI, ONO and OKAMOTO, 1979, Pl. 4, fig. 7 ; ITOIGAWA, SHIBATA,
NrsHIMOTO and OKUMURA, 1981, Pl. 34, figs. 10a-b, 14a-b.
Description. : Shell rather small, globose. ' Spire somewhat elevated_, higher than
diameter. Whorls convex, about 4 in number ; body-whorl very large. Suture deeply
impressed. Aperture semilunular, oblique downward. Umbilicus open ; callus pad
undeveloped .
Dimensions :
DGSU coll. cat. no.
T1713 T1714 T1715
(Tanaka's specimen)
Height (mm) ro.5
12.7
l 5.0 +
1 1 .o
Diameter (nun)
9.4 1 1 .O
14.0
8.5
Remarks : This species has been reported from verious localities in Japan and the
Korean Pemnsula. Though the specimens at hand are small in size compared with
those from other localities, they can be identified with this species by their obtusely
shouldered whorls, rather fiattened body-whorl and umbilical characters
Genus Neverita RISSO, 1 826
subgenus Glossaulax PILSBRY, 1 929
Neverita (Glossaulax) cf. coticazae (MAKIYAMA, 1 926)
(Pl. I, figs. 4, 5)
Polinices (Neverita) coticazae MAKIYAMA, 1926, p. 150 Pl. 12, fig. 8 ; NoMURA, 1939, p. 255. P1. 13,
figs. 13a-14b.
Polinices coticazae MAKIYAMA, KANNO and OGAWA, 1 964, Pl. 2, fig. 1 2
Neverita coticazae (MAKIYAMA), KA~ADA, 1 962, p. 1 57, P1. 1 8, figs. 2la-22 ; MASUDA and TAKEGAWA,
1965, P1. 2, fig. 21 ; MASUDA, 1967, p. 5, Pl. I , figs. 25a-26b ; KOTAKA and NoDA, 1967, Pl. 1, figs
1 3, 16; ITOIGAWA, SruBATA and NISHIMOTO, 1974, p. 148, Pl. 45, figs. 5, lOa-b ; TAGUCHI, ONO
and OKAMOTO. 1979, Pl. 4, figs. 4, 5
Neverita (Glossaulax) coticazae , (MAKIYAMA), ITOIGAWA, SHIBATA, NISHIMOTO and OKUMURA, 1 981,
Pl. 34, figs. 2a-b.
Description : Shell small, globose. Spire low ; body-whorl very large. Suture
shallow, rather inconspicuous. Aperture slightly oblique downward. Umbilicus not so wide ; callus pad rather heavy, transversely grooved
Dimensions :
96
DGSU coll. cat. no.
Katsurm TArcAYASU
Height (mm) Diameter (mm) 1 1 .o
ca. 9.5
Remarks : The present specimens closely resemble N. coticazae in genetal fe_atures,
but they are small in size and slightly differ from the latter in the umbilical features
Order NEOGASTROPODA Family MELONGENIDAE
Genus Hermfusus SWAlNSON, 1 840
Hemihusus ? mimasakensis (YOKOYAMA, 1 929)
strombus mimasakensis YOKOYAMA, 1929, p. 366, P1. 70, figs. Ia-b.
Description : Shell large, thick and solid, Iacking the upper portion of the spire
Body-whorl relatively well preserved except the outer lip, about 9 5 mm high and
85 mm m maxrmum diameter, with large spinose tubercles on the shoulder ; tubercles
rather prominent and acute, nine in number on the body-whorl. External surface
of the body-whorl running longitudinally numerous distinct growth lines, the lower
half ornamented inahy spiral cords of irregular inagnitude, and the upper half having
n0. distmct ornamentation except a row of shoulder spines. -Siphonal canal rather
short, fasciole stout. Inner lip covered with comperatively thick callus., Only one
speimen (DGSU coll. cat. no. T1797) is at hand
Remarks : This species was first described by YOKOYAMA ( 1 929) from the Bihoku
Group in the Tsuyama basin, Okayama Prefecture. The type specimen shown in the
original paper lacks the apex as well as the lower portion of the body-whorl. The
careful observations of the external surface. of the present specimen reveal that the
longitudinal growth lines on the body-whorl show only the gentle curve with shallow
lateral sinus at the shoulder spinose row, and some remains of notch or a sinus band
can not be observed on the lower potion of the body-whorl. In other words, none of
the traces of "stromboid notch" characterizing the stromboid shells are observable
on the external surface of the body-whorl. Therefore, the original generic name,
Strombus, is not adopted presumably for this species
The present species is closely allied to Henafusus cochlida (LlNN~), a living species
of the tropical Indo-Pacific, in having rather short siphonal canal, many irregular,
round-topped spiral cords on the lower half of the body-whorl and no distinct sculpture
except a row of spinose tubercles on the upper half of the body-whorl. However,
the former is about double as large as the latter. It also resembles Volema osaw-
anoensis TSUDA (1959) from the Kurosedani Formation, Toyama Prefecture, in the
characteristics of the spiral cords, but the former has more acute tubercles and its
external surface of the body-whorl is not wrinkled. Melongena sazanami KANEHARA
(1937) from the Bihoku Group in Okayama Prefecture is distinguished_ from the
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda Crty 97
present species in having numerous spiral cords of regular magnitude developed on the
entire surface of the whorl
Class BIVALVIA
Subclass PALAEOTAXODONTA
Order NUCULOIDA
Family NUCULIDAE Genus Acila H. & A. ADAMS
Subgenus Acila, s.s
Acila (A cila) sublnirabilis MAKIYAMA, 1 926
(Pl. II, fig. 6)
Acila submirabilis MAKIYAMA, 1 926, pp. 151-1 52, P1. 12, fig. 9 ; HAYASHI and MIURA, 1973, Pl. 1,
fig. 2 ; HAYASHI, 1 973, Pl. 5, fig. 4 ; ITOIGAWA, SHIBATA and T~ITISHIMOTO, 1 974, p. 46, NISHIMOTO
Pl. 1, figs. 9a-14b ; TAGUCHI, ONo and OKAMOTO, 1 979, Pl. 1, figs. IJ!:; ITOIGAWA, SHIBATA
and OKUMURA, 1981, Pl. 1, figs. 3a~~b.
Acila (Acila) submirabilis MAKIYAMA, WATANABE, ARAI and HAYASHI, 1 950, Pl. I , fig. 2 ; KANNO, 1 960,
p. 190, P1. 31, figs. 3-7 ; OKAMOTO, TAI~HASHI and TERACHI, 1973, Pl. 14, fig. Ia-b
Remarks : The specimen obtained is a ill-preserved right valve, but the posterior
ridge and divaricated threads on the shell surface are remarcable. DGSU coll. cat.
no. T1733 ; height 15.2 mm, Iength 20.0 mm+ , depth 5.0 mm+
Subclass PTERIMORPHIA
Order ARCOIDA
Family ARCIDAE
Subfamily ANADARlNAE Genus Anadara GRAY, 1 847
Subgenus Hataiarca NoDA, 1 966
Anadara (Hataiarca) daitokudoensis (MAKJYAMA, 1 926)
(Pl. II, figs. 2-5b)
Arca (Anadara) daitokudoensis MAKIYAMA, -1926, pp. 153-1 54, Pl. 2, figs. lO, 14-d 5
Anadara daitokudoensis (MAKIYAMA), OTUKA, 1938, p. 25, Pl. I figs. 3~$
Anada,'a (Hataiarca) daitokudoensis (MAKIYAMA), NoDA, 1966, p. 1 15, Pl. 7, fig. 13; OKAMOTO and
and TERACHI, 1 974. Pl. 47, figs. 5a-7b ; ITOIGAWA, SHIBATA and NISHIMOTO, 1 974, p. 57, Pl. 4,
figs. 10a-b; TAGUCHI, ONo and OKUMOTO, 1 979, P1. 1, figs. 8, 9.
Description : Four mould specimens of attached valves and several fragments of
shell materials are at hand. Shell medium in size, rather convex. Cardinal profile
rather flat. Anterior end short, regularly rounded ; posterior end sharply rounded
S_ culpture cQnsisting 26 to 28 nQn-dichotomous? g_ ranulated, narrow, equal radial
98 Katsuml TAKAYASU ribs. Muscular scar strongly impressed,
strongly crenated
Dimensions :
subquadrate in shape. Interior margin
DGSU coll. Height Length De pth Length of A pical Number cat. no. (mm) (mm) (nlm) ligament (mm) angle of ribs
T1729 (right) 13.2 17.0 6.0 10.9 86 26 T1793 (core) (33.6) (44.3) (28 . 8/2) 28.8 88 28 T1794 (core) (22.8 +) (3 5 .o) (ca. 20.2/2) ca. 24.0 ca. 80
T1795 (core) (16.5+) (23.0) (ca. 14.7/2) 14.7 81 27 T1796 (core) (17.3) (2'~. 5) (14.3/2) ca. 14.0 85 28
Remarks : Young form of the present species is somewhat allied to Anadara (Scaphaca) abdita MAKIYAMA, a Miocene Anadara frecuently associated with Anad.
daitqkudoensis, but the present species is distinguished by its convex shell and its
small number of radial ribs.
Subfamily STRIARClNAE
Genus Striarca C0.NRAD, 1 862
Striarca uetsukiensis (HATAI and NISIYAMA, 1 949)
(Pl. II, figs. 7a-c)
Barbatia (Barbatia) uetsukiensis HATAI and NISIYAMA, 1 949, p. 89, P1. 23, figs. 6-7 ; UOZUMI and FuJIE,
1966, pp. 144~145, Pl. 11, figs. 2, 3.
Barbatia cf. uetsukiensis HATAI and NISIYAMA, MASUDA, 1 955, P1. 1 9, fig. 1
Striarca uetsukiensis (HATAI and NISIYAMA), NoDA, 1 966, p. 74, Pl. 4, figs. 1-3, Pl. 1 1 , fig. 4 ; ITOIGAWA,
SHIBATA and NISHIMOTO, 1 974, p. 56, P1. 4, figs. 6a-b ; TAGUCHI, ONO and OKAMOTO, 1 979, Pl. I ,
fig. Il.
Description : Shell small, quadrated, rather convex. External surface with fine
radial ribs crossed by concentric growth lines. Ligamental area narrow, elongated,
with numerous longitudinal striations. Teeth arrangement not clear by ill presevation
Inner margin not crenated
Dimensions :
DGSU coll. cat. no.
T1727 (right valve)
T1792 (right valve)
Height (mm) Length (mm) Depth (mm) ca. 13.5
15.8
21 .5
23.7
7.4
8.0
Remarks : The present specimens are rather large in size compared' with the same
species from other localities ; for example, the specimen from the Mizunami Group is
7.6-8.0 mm high and 10.4-11.5 mm long (ITOIGAWA, SHIBATA and NISHIMOTO, 1 974)
But other features of the specimens frQm the M~sud~ Group are well identic~l writh_
S,=_ . ~letsuk~fensis,
Fossil Molluscs from the Miocene Masuda 'Group at Okuda, Masuda City 99
Order PTERIOIDA
Family OSTREIDAE
Subfamily OSTRElNAE
Genus Crassostrea SACCo, 1 897
Crassostrea gravitesta (YOKOYAMA), 1 926 (Pl. 11, fig. 1 5)
Ostrea gravitesta YOKOYAMA, 1926, p. 388, P1. 45, figs. 1, 2; NoMURA, 1938, p. 248, Pl. 33, fig. 15;
KASENO, 1956, p. 5. Pl. 1, figs. 5a-c; OGASAWARA, 1973, Pl. 13, fig. 28; HAYASHI, 1973, PI. 2,
fig. 5.
Crassostrea gravitesta (YOKOYAMA), ITOIGAWA. SruBATA and NISHIMOTO, 1 974, p. 72. Pl. 1 7, fig. I ;
ITOIGAWA and NISHIKAWA, 1976, P1. 33, fig. 1 1 ; TAGUCHI, ONO and OKAMOTO, 1979, Pl. 1, fig. 15; AMANO, 1980, p. 106, Pl. 13, figs. 29a-b.
Relnarks : An imperfect specimen (DGSU coll. cat. no. T1734) is at ahd. As already
mentioned, this species is swarmed in a few beds of the lower horizon of the outcrop.
Shells are irregulary piled up each other, and it is difficult to sample a perfect specimen
Subclass HETERODONTA
Order VENEROIDA
Family CARDIIDAE
Subfamily TRACHYCARDIINAE Genus Vasticardium IREDALE 1 927
" Vasticardium" ogurai (OTUKA, 1938)
(P1. II, fig. 9)
Cardium (Bucardium) ogurai OTUKA, 1938, pp. 28-29, Pl. ' 1, figs. 1, 2, 8.
Vasticardium ogurai (OTUKA), SHuro, 1960, p. 213, P1. 25, figs. 13, 16; OGASAWARA, 1973, p. 143,
Pl. 12, figs. 12, 13.
"Vasticardium" cf. ogurai (OTUKA), ITOIGAWA, SHIBATA and NISHIMOTO 1 974 p 8 1 P1 21 figs 2 3.
"Vasticardium" ogurai (OTUKA), ITOIGAWA and NISHIKAWA, 1 976, Pl. 34, fig. 3 ; ITOIGAWA SrnBATA
NISHIMOTO and OKUMURA, 1981, Pl. 11, fig. 9
Description : Specunen preserved as almost inner mould, but a small fragment of
shell material remaining on the margin. Shell medium in size, subtrigonal, inflated ;
antero-dorsal margin rounded ; postero-dorsal margin rather straight, slightly longer
than the antero-dorsal margin. Surface sculptured with about 39 radial ribs ; radial
ribs fiat-topped, nearly equal in width to the interspaces
Dimensioil~ : '
DGSU coll. cat. no
.. ･T1728 (core)-
Height (mm) (27･O)
Length (mm) . (28,4)
Depth (mm) (1 8.812)
lOO Katsuml TAKAYASU Remarks : The inner mould of this species is at a glance like that of the young form of
Clinocardium shinjiense (YOKOYAMA, 1 923) from the upper Miocene Fujina Formation
in Shimane prefecture, but the former is distinguished from the latter by its more
promment umbo, flat-topped radial ribs and shallow interspaces
Family CARDILIIDAE Genus Cardilia DESHAYES, 1 835
Cardilia toyamaensis TsuDA, 1 959
(P1. II, figs. 10aHc)
Cardilia toyamaensis TsuDA, 1959, p. 79, P1. 3, figs. 6a-9 ; MASUDA, 1966, P1. 35, figs. 38a-b; ITOIGAWA,
SHIBATA and NISHIMOTO, 1974, p. 95, Pl. 28, figs. 1, 2; TAGUCHI, ONo and OKAMOTO, 1979, Pl. 3,
figs. 1-3 ; ITOIGAWA, SHIBATA, NISHIMOTO and OKUMORA, 1981, P1. 18, figs. 2a~.
Description : Shell small in size, very inflated, Iongitudinally elongated. Beak
anteriorly situated, roundly incurved toward the anterior side. Surface sculptured
with irregular con centric wrinkles ; posterior half of the surface with flat-topped radial
ribs ; interspace between radial ribs narrow and shallow.
Dimensions :
DGSU ccill. cat. no.
T1791 (core) Herght (mm) Length (mm) Depth (mm)
(17.2) (1 1 .8) (15.5/2)
Remarks : The shell material of this specimen is almost dissolved out. But it is
very thin in original, therefore the sculptures on shell surface are comparatively well
unpressed on the mould. The characteristics of the present specimen are entirely
identical with those of the type specimen originally described by TSUDA ( 1 959) excepting
that the former is about I . 5 times large as the latter.
Family DONACIDAE Genus Latona SCHUMACHER, 1 8 1 7
Latona sp.
(Pl. II, fig. 8)
Description : Shell medium in size, flat, trigonal ; beak small, situating posteriorly ;
anterodorsal margin long, straight ; posterodorsal margin short, slightly rounded
External surface with rather irregular growth lines ; internal sl4rface unknown in this
specamen Dimensions :
DGSU coll. cat. no. Henght (mm) Length (mm) Depth (tnm) T1790 (right valve) 19.7 27 . 7 ca. 6.0
Remarks The present specm~_n ~S_ _ di.Stingujshe.. ~ f.rQr~ ~a_tonq m. inQ~n~~s___ ITQIG_.AWA
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda City lol
from' the Miocene Mizunami Group by its large size and less rounded posterodorsal
margm
Family TELLlNIDAE
Subfamily TELLlNlNAE
Genus Fabulina GRAY, 1 8 5 1
"Fabulina" sp.
(Pl. II, fig. I l)
Description : Shell small in size, trapezoidal ; beak small, pointed, situating
posteriorly ; anterodorsal margin I ong, slightly rounded ; posterodorsal margin short,
rather straight ; anterior margin moderately rounded ; posterior margin truncated ;
ventral margin rather straight. External surface weathered and being opaque
Dimensions :
DGSU. coll. cat. no.
T1789 (conjoined)
(Tanaka's specimen
conjoined)
Height (mm) 13.5
13.6
Length (mm) ' 20.3
20.3
Depth (mm) 7.1/2
6.5/2
Remarks : Because of their fragilely weathered shells, detail .features are not ob-
servable. The precise identification depends on future researches
Subfamily MACOMlNAE Genus Macoma LEACH, 1 8 1 9
Subgenus Macoma s.s
Macoma (Macoma) izurensis (YOKOYAMA, 1 925) (Pl. II, figs. 12a-14)
Tellina izurensis YOKOYAMA, 1925, p. 19, Pl. 2, fig. 12.
Macoma izurensis (YOKOYAMA), KAMADA, 1962, p. 132, Pl. 15, figs. 7-9; KANNo and OGAWA, 1964,
P1. 2, figs. 4, 5 ; MASUDA and TAKEGAWA, 1965. Pl. 2, figs. 6a-7; HAYASHI and MIURA, 1973, Pl. I ,
figs. 23, 24; HAYASHI, 1973. Pl. 4, fig. 13, Pl. 6, fig. 6 ; ITOIGAWA, SHrBATA and NISHIMOTO, 1 974,
P1. 30, figs. Ia-11.
Macoma (Macoma) izurensis (YOKOYAMA), ITOIGAWA, SHIBATA, NrsmMoTo and OKUMURA, 1 981, Pl. 1 9
figs. 2la-b.
Description : Shell small in size, ovate, relatively inflated in the anterior portion ;
fold running from beak to posteroventral margin on the ~ Ieft valve ; posterior margin
slightly turned tp right ; beak s~tuating somewhat posteriorly. Pajlial sinus . 1~. rge,
dee p.
Dimensions_ : -
l 02 Katsurm TAKAYASU
DGSU coll. cat. no. Height (mm) I Length (mm) Depth (mm) Tl 730 (conjoined) 14.9 22. 1 6.0/2
T1731 (left int. mould) 14.6 ca. 22.0
T1788 (conjoined) 18.8 25.0 8.9/2
(Tanaka's specimen- 1 14.7 22.6 ca. 3.5
left valve)
(Tanaka's specimen-2 16.9 24.8 4.0 left valve)
Rem,arks : Though the specimens at hand are very small in size compared with the
YOKOYAMA'S type specimen, their slightly concaved posterodorsal margin and relatively
elongated ovate outline are in good agreement with the characteristics of that species.
All of the examined specimens are drilled by some carnivorous animals, therefore they
may be the young form ; the small shells of M. izurensis illustrated by ITOIGAWA, SHIBATA
and NISHIMOTO (1974, pl. 30, figs. 7-lO) closely resemble the present specimens
Family CULTELLIDAE Genus Cultellus SCHUMACHER, 1 8 1 7
Culutellus izumoensis YOKOYAMA, 1 923
(Pl. 111, figs. 10, 1 1)
Culutellus lzumoensrs YOKOYAMA 1 923 p 5 P1 2 fig I OTUKA 1941, pp. '23-24, fig. 4, ; KANNo 1956, p. 213, P1. 6, fi~･ 8･; IwAI, 1961", pl. '1, fig. i9; iwAI, 1965, p. 45, Pl. 12-; U6~UMI and FuJIE,
1966, p. 153, Pl. 12, fig. 7; HAYASHI and MIURA, 1973, Pl. l, fig. 22; ITOIGAWA, SHIBATA and
NISHIMOTO, 1974, p. 101, Pl. 31, fig. 4, 5;' OGASAWARA; 1976, p. 57, Pl. 4, figs. 16, 18; SUEHlRO,
1979, p. 83, P1. 14, figs. 4a-b,; OGASAWARA and NoMURA, 1980, p. 89, Pl. Il, figs. 5a-b, 9; ITol-
GAWA, SHIBATA, NISHIMOTO and OKUMURA, Pl. 20, figs. 3a-b
Cultellus izumoensis izumoensis YOKOYAMA, AMANO, 1 980, pp. 1 10-111, P1. 1 3, fig. 23
Phaxas cf. izumoensis (YOKOYAMA). MASUDA, 1955, Pl. 19, figs. 14a-b.
Description : An inner mould and a fragmental specimen are obtained. Shell medium in size, compressed, transversely elongated ; beak situating anteriorly ; post-
erior side about four times as 16ng as the anterior side ; anterior margin broadly
rounded ; posterior margin rather sharply rounded
Dimensions :
DGSU coll. cat. no.
T1732 (core) ti781 (fragment)
Herght (mm) Length (mm) Depth (nun) . (24.8) (8 1 .5) (9･5/2)
Re;narks : The present specimen resembles C. izumoensis jobanicus KANNO (1956)
in having slightly concaved ventral margin, but is distinguished therefrom by its more
rounded anterior margin ; the concaved ventral margin is probably only an appearance
Qwing to the preservation of an inner mould. Cultellus rectangulas KANNO (1956) is
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda City 103
another alled species, but its posterior margin is subtruncated.
Family VENERIDAE
Subfamily CYCLlNlNAE
Genus Cyclina DESHAYES, 1 850
Cyclina takayamai OYAMA, 1950 (Pl. 111, fig. 2)
CJ,clina sinertsis GMELIN, OTUKA, 1938, PP･ 3'--33, Pl. 12, figs. 13, 1 5.
Cyclina takayamai OYAMA, 1 950, p. 2.
Cyclina takeyamai OYAMA, ITOIGAWA and NISHIKAWA, 1976, Pl. 34, fig. 9
Cyclina (Cyclina) takeyamai OTUKA, TAGUCHI, ONo and OKAMOTO, 1 979, Pl. 2, figs. 1 7, 1 8
Description : Shell medium in size, suborbicular, moderately inflated ; beak small
pointed, oblique anteriorly ; antrodorsal margin short, concaved ; posterodorsal margin
long, broadly rounded. External surface almost smooth except very weak fine radial
stiriations and faint fine concentric growth lines ; in the case of weathered surface, fine
radial ribs rather remarkable. Whole of interior margin weakly crenated
Dimensions :
GDSU coll. cat. no. Helght (mm) Length (mm) I Depth (mm) T1787 (left valve) 30.9 29. 1 l0.1
Remarks : The present specimen very resembles C. japonica KAMADA (1952) in outline, but the former is distinguished from the latter by its small slze and rts very
weak surface sculptures.
Cyclina ? hwabongriensis YooN and NoDA, 1 976
(Pl. 111, figs. Ia-b, 3-8b.) -
Cyclina (Cyclina?) hwabongriensis YOON and NoDA, 1 976, PP. 29-3 1 , figs. 2-5 ; TAGUCHI, ONO and
OKAMOTO, 1979. Pl. 2, figs. 19-23.
Description : Shell moderate to large in size, suborbicular, generally a little longer
than high, moderately inflated ; beak small, but not so much pointed ; anterodorsal
margin slightly concaved, Ionger than posterodorsal margin ; posterodorsal margm
broadly rounded, forming a blunt angle with posterior margin. Sculpture consrstmg
of fine numerous, concentric growth-lines and weak radial ribs on the anterior surface
Anterior part of the interior margin crenated ; the other part of the interior margm
smooth. Paliial sinus triangula~, round~d at end.
Dimenstons ; -
104 Katsumi TAKAYASU
DGSU coll. cat. no.
T171 7 (conjoined)
T1718 (conjoined)
T1719 (conjoined)
T1720 (core)
T1721 (core)
T1722 (conjoined)
T1723 (core)
T1724 (core)
T1782 (core)
T1783 (conjoined)
T1784 (conjoined)
T1785 (conjoined)
T1 786 (conjoined)
Tanaka's specimen-1 (core)
Tanaka's specimen-2 (core)
Height (mm)
28.3
39.0
32.2 (28 .O)
(33.8)
22.9 (21 .5)
(16.8)
(19.6)
ca. 24.4 46 . 3
644.5 5-5.9
(43 . I )
(39.6)
Length (mm)
32.4 43 , 8
35.0
(32.3)
(36.8)
24.4 (,~5.5)
(_17.0+)
(21.8)
28.2 47 . 7
49.5
ca. 52.8 (46.2)
(41 . 7)
Depth (mm)
1 7.2/2
24.5/2
1 2.9/2
(15.7/2)
(17.8/2)
1 1 ･8/2
(ro.5/2)
(9 ･ 3/2)-
(ro.1/2)
1 3･2/2
15.6+/2 26.8/2
31.5/2
(24.0/2)
(22.3/2)
Depth of pallial
sinus (mm)
1 1 .5
10.9 1 1 .O
8.5
8.2
5.8
7.8
13.1
14.8
Remarks : The present specimens closely resemble C. (Cyclinorbis) Iunulata MAKI-
YAMA (1926) ; the original description and the remarks by KAMADA (1952) of lunulata
are almost applic~ple to .them. The lunple-like sculpture characterizing that species
is also observable in some specimens from the Masuda Group. ' However, the speci-
mens at hand are slightly different from lunulata in having rather blunt end of pallial
sinus and weak radial ribs on the anterior surface.
Order MYOIDA
Family CORBULIDAE
Subfamily COLBULlNAE Genus Anisocorbula IREDALE, 1930
Anisocorbula osawanoensis TSUDA, 1959
(Pl. 111, figs. 9a-b)
Anisocorbula osawanoensis Tsul)A, 1 959, p. 79, P1. 3, figs. roa~.
Description : Shell small, thick, infiated, with strong, round-topped, concentric
ribs ; posterior end rostrate, bluntly pointed ; anterior end rounded ; right valve slightly
larger than the left and overlapping the latter
Dimensions :
DGSU coll. cat. no. Helght (mm) Length (mm) Depth (mm) T1725 (conJOined)
T1726 (conjoined)
(Tanaka's specimen, con j omed)
8.8
8.l
6.6
13.6
12.5
8.9
8.3
8.0
5.2
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda Crty 105
Remarks : ' This species somewhat ･resembles Solidicorbula succincta (YOKOYAMA,
l 924), a species already reported from the Setouchi province (ITOIGAWA, SHIBATA and
NISHIMOTO, 1974 ; TAGUCHI, ONO and OKAMOtO, 1979), in having coarse, strong, con-
centr.ic ribs, but the former is distinguished from the latter by its oblong outline and
its small umbo
Ref erences
AMANO, K., 1 980; Miocene Molluscan Fossils .the Yudoro Formation in the East of Rumoi, Hok-
kaido. Prof･ S. Kanno Meln. Vol. 99L120, Pl. 1 3.
ARAKI, Y., 1 960 ; Geology, P~leontotogy and Sedimentary Structures (including Problematica) of
the Tertiary FormatiQns Developed in the Environs of Tsu City, ,Mie:Prefecture, Japan. Bull.
Lib. Arti pep., Mie Univ.. Spec. Vol., no. 1, 3-1 18, Pls. 1-1 1.
FUJIE, T. and UozuMI, S., 1 957; Illustrated Cenozoic Fossils, 25. Changes of the Neogene Fauna
m Hokkaido (Preliminary Report). Pt. I . Outline of Fossil Cominunities and Their Geological
Distribution (in Japanese). Cenoz. Res., no. 23, 499-504, Pl. 24, 2 text-figs
FuJrrA, T., 1964; Geology of the Northem Area of Masuda City, Shimane Prefecture. With Special References to the Neogene Formations (in Japanese with English abstract). Jour
Geol. Spc. Japan, vol. 70, 100-109.
HATAI, K. and NlSIYAMA, S., 1'949 ; New Tertiary Mollusca fron) Japan. Jour. Paleont., vol. 23,
no. 1, 87-94, Pls. 23, 24.
HAYASAKA, S.; 1 969 ; Molluscan "Fauna of the Kukinaga Gtoup' in Tan~-ga-shima, South Kyushu
Japan. Rep. Fac. Sci.. Kagoshima Univ., no.'2, 33L52, pls. 1-3,' I text-fig. .
HAYASHI, T., 1 973 ; Fossils from the Environs of Horaiji-san (in Japanese). Bull. Horcajisan Nat
Sci. Mus., 10-17, Pls. 1-6, I text-fig.
and MIURA, Y., 1 973 ; The Cenozoic Sediments in the Southern Part of Okazaki City,
Central Japan (in Japanese with English abstract). Bull. Aichi Univ. Educ,, vol. 22, Nat. Sci.,
133-149; Pls. 1, 2, 7 text-figs.
IKEBE, N., 1939; On Certain Specimens of Vicarya. Jour. Geol. Soc. Japan, vol. 46, no. 553, 542-
546, 7 text-figs.
ITOIGAWA, J., 1 956; Molluscan Fauna of the Tsuzuki Group in Kyoto Prefccture, Japan. Mem Coll. Sci.. Univ. Kyoto. Ser. B, vol. 23, no. 2, 179-192, Pls. 1-3, 2 tex-figs.
and NISHIKAWA, I., 1 976 ; A Few Pioblems on the Miocene Setouchi Series in the Northern
Part of Okayama-Hiroshima Prefectures, Southwest Japan (in Japanese with English abstract)
Bull. Mizunami Fossil Mus., no. 3, 127-149. Pls. 33-35.
and SHIBATA, 1 976; Twelve New Gastropos from the Miocene Mizunami Grouop, Gifu Prefp.cture, Japan. Ibid., no. 3, 5-15, Pls. 2, 3
and NISHIMOTO, H., 1 974 ; Molluscan Fossils of the Mizunami Group. (in Japanese). Ibid., no. 1,43-203, Pls. 1-63, 5 text-figs
and Okumura, K., 1 981; Miocene Fossils of the Mizunami Group, Central Japan. 2. Molluscs (in Japanese). Monogr. Mizunami Fossil Mus., no. 3-A, 1-53, Pls
1 -52.
IWAI, T., 1 961 ; The Miocene Molluscan Fossils frdm the Area Southwest of Hirosaki~City, Aomori
Prefecture, Japan. Trans.' Proc. Palaeont. Soc. Japan. N.-S;. no. 41, 1-8, Pl. l; I text-fig
, 1 965 ; The Geological and Paleontological Studies in the Marginal Area of the Tsugaru
Basin, Aomori Prefecture, Japan. Bull. Educ. Fac.. Hirosaki Univ., no. 15, 1-68. Pls. 12-20,
3 text-figs.
106 Katsunu TAKAYASU KANEHA!~, K., 1 937; On Some Neogene Shells from Japan, Part I . Jour. Geol. Soc. Japan, vol. 44,
781-785, Pl. 23.
KAMADA, Y. ; 1 952; On Some Species of Cyclina from Japan and Korea. Trans. Proc. Palaeont
Soc. Japan. N.S., no. 6,~ 167-173, Pl. 15,
, 1 960 ; ･- On the Associated Occurence of Vicarya and Vicaryella in the Japanese Tertiary,
with the F~irst Description of a Paleogene Species of Vicarya from Japan. Sci. Rep.. Tohoku
Univ., 2nd Ser,, Spec. Vol., no, 4 (Hanzawa Mem. Vol.), 281-295, Pls. 30, 31.
, 1962; Tertiary Marine Mollusca from the Joban Coalfield, Japan. Spac. Pap., Palaeont
Soc. Japan, no. 8, 1-187, Pls. 1-21, 3 text-figs.
KANNo, S., 1956; Fossil and Recent Species of Cultellid Molluscs from Japan. Sci. Rep., Tokyo
Kyoiku Daigaku. Sec. C, vol. 4, no. 34, 209-218, Pls. 5, 6.
, 1 960 ; The Tertiary System of the Chichibu Basin, Saitama Prefecture, Central Japan
Part II. Palaeohtology. Japan Soc. Prom. Sci., 123-396, .pls. 31-51, 6 text-~gs.
and OGAWA, H., 1 964 ; Molluscan Fauna from the' Momijiyama and Takinoue Districts, Hokkaido, Japan. Sci. Rep.. Tokyp Kyoiku Daigaku. Sec. C, vol. 8, 269-294, PI~. 1~; 5 text-
KASENO, Y., 1 956; Illustrations of Fossils from Fukui. Pt. I . The Vicinity of Ayukawa (in Japanese)
Sci. Colnm. Fukui City and Fukui City Mus., 1-16, Pls. IJS, 4 text-figs.
KOTAKA, T. and NoDA, H., 1 967 ; Miocene Mollusca from the Minami-Tsugaru District, Aomori Prefecture, Northeast Japan.. Saito Ho-on Kai Mus., Res. Bull., no. 36, 33~S7, Pls. 1, 2
MAKlYAM4, J., 1926; Tertiary Fossils from North Kankyo-do, Korea. Mem. Col!. Sci., Kyoto Imp. Univ.. Ser. B, vol. 2, no. 3, 143-160, Pls. 7, 8.
MASUDA, K,, 1955; Miocene Mollusca from Noto Peninsula, Japan. Part I (1). Trans. Proc. Pa-
laeont. Soc. Japan. N. S., no. 20, 1 19-127, Pl. 19.
, 1956; Ditto. Part I (2). Ibid., no. 21, 161-167, Pl. 26.
, 1 966 ; Molluscan Fauna of the Higashi-Innai Formation of Noto Peninsula, Japan, II
Remarks on Molluscan Assemblage and Description of Species. Ibid., no. 64, 3 1 7-337, Pls
35, 36, 6 text-figs.
, 1 967 ; Ditto. 111. Description of New Species and Remarks on Some Species. Ibid., no.
65, 1-18; Pls. 1, 2.
and TAKEGAWA, H., 1 965; Remarks on the Miocene Mollusca from the Sennan District,
Miyagi Prefecture, Northeast Honshu, Japan. oaaito Ho-on Kai Mus. Res. Bull., no. 34, 1-14,
Pls. I , 2, ･ I text-fig.
MlzUNO, A., 1 964 ; A Study on the Miocene Molluscan Faunas of the Kitatsugaru and Nishitsugaru
Districts, North Honshu. Bull. Geol. Surv. Japan, vol. 1 5, no. lO, 595-622, Pls. 1~, 4 text-figs
NoDA, H., 1966 ; The Cenozoic Arcidae of Japan. Sci. Rep., Tohoku Univ., 2nd Ser., vol. 38, no. 1,
1-161, Pls. 1-14, 16 text-figs.
NoMURA, S., 1 935; Miocene Mollusca from Siogama, Northeast Honshu, Japan. Saito Ho-on
Kai Mus. Res. Bull., no. 6, 193-234, Pls. 16, 17.
, 1 938; Molluscan Fossils from the Tatsunokuti Shell Bed Exposed at Goroku Cliff in the
Western Border of Sendai. Sci. Rep. Tohoku Imp. Univ., Ser. 2, vol. 19, no. 2, 235-･-75, Pls
33-36.
, 1939; Miocene Mollusca from Yamaguti, Kozai-Mura. Igu-Gun, Miyagi-Ken, Northeast
Honshu, Japan. Jour. Geol. Soc. Japan, vol. 46, 253-257, Pl. 13
OGASAWARA, K., 1 973 ; Molluscan Fossils from the Nishikurosawa Formation, Oga Peninsula
Akita Prefecture, Japan. Sci. Rep. Tohoku Univ., 2nd Ser., Spec. Vol., no. 6, 137-155, Pls.
12, 13. ~
1976 Mrocene Mollusca from Ishikawa Toyama Area Japan lbid vol. 46, no. 2, 35-78,
Fossil Molluscs from the Miocene Masuda Group at Okuda, Masuda City 107
Pls. 11-15.
and NoMURA, R. ., 1 980; Mollusca from the Fujina Formation, Shimane Prefecture, San-in
District, Japan. Prof･ S. Kanno Mem. Vol., 79-98, Pls. 9rl2.
OKAMOTO, K. and TERACHI, M., .1974･; Miocene Molluscs from the Bihoku Group at Miyauchi-cho,
Shobara City, Southwest Japan. Trans. Proc. Palaeont. Soc. Japan, N. S., no. 9.5, 341-352,
Pl. 47, 2 textlfigs.
OTUKA; Y., 1 934; . Tertiary Structure of the Northeastern End of the Kitakami Mountainland, Iwate
Prefecture, Japan. Bull. Earthq. Res. Inst., vol. 1'_, pt. 3, 566T638. Pls. 44-51
, 1938; Mollusca from the Miocene of Tyugoku, Japan. Jour Fac Sa Imp Umv Tokyo Sec. 2, vol. 5, pt. 2, 21~~5, Pls. I~~.
, 1 941 ; Fossil Mollusca from ' Tazima, Hyogo Prefecture, Japan. Jap. Jour. Geol. Geogr. ,
vol. 18, nos. 1-2, 21-24.
OYAMA, K., 1 950 ; Remarks on Japanese Fossil Molluscan Name (.in Japanese). ･ Miner. and Geol..
vol. 3, no. 6, 225-228.
SArro, M., 1962 ; The Geology of Kagawa and Northern Ehime Prefectures, Shikoku, Japan. Mem
Fac. Agr.. Kagawa Univ., no. 10, 1-74, Pls. 1-17, 5 text-figs.
SHJKAM:A, T., 1 954 ; On the Tertiary Formations of Tomikusa in South Nagano Prefecture (in
Japanese with English abstract). Sci. Rep., Yokohama Nat. Univ.. Ser. 2, no. 3, 71-108, Pls
I~8, 3 text-figs.
SHUTO, T., 1 960 ; Cardiids from the Miyazaki Group (Palaeontological Study of the Mryazaki
Group-VII). Trans. Proc. Palaeont. Soc. Japan. N. _ S:, no. 37, 209-222,' Pl. 25, 2 text-figs.
SUEHIRO, M., 1 979 ; Upper Miocene Molluscan Fauna of the Fujina Formation, Shimane Prefecture,
West Japan (in Japa;lese with English abstract). , Bull. Mizuhami Fossil Mus., no.~ 6, '65-100,
Pls. 10-16, 2 text-figs.
TAGUCHI, E., ONo, N. and OKAMOTO, K., 1 979 ; Fossil Molluscan A~semblage~ from the Miocene
Bihoku Group in Niimi City and Ohsa-cho, Okayama Prefecture, Japan (in Japanese with English abstract). Ibid., 1-15, Pls. 1~, 3 text-figs
TAKEYAMA, T., 1 933; Notes on the Genus Vicarya, with Descnption of Two Japanes Forms. Jap
Jour. Geol. Geogr., vol. lO, nos. 3~, 129-144, P1. 13.
TANAKA, I., 1981 ; Vicarya Found ' by Students of a Jounior High School. in "Tales of Fossils in
San m Dlstnct (SANlN KASEKI MONOGATARI)", ed. by Okubo, M. and Akagi, S. (in Japanese, original title translated), 1 52-162, Tatara Shob~, Yonago
TsuDA, K., 1959 ; New Mlocene Molluscs from the Kurosedani Formation In Toyama Prefecture, Japan. Jour. Fac. Sci.. Niigata Univ., 2nd Ser., vol. 3, no. 2, 67-110, Pls. 1-7.
, 1 965; Neogene Molluscan Assemblages in the Inner Zone of Northeast Japan with
Special Reference to Middle Miocene Assemblages (in Japanese). Fossils, no. 10, 20-23, 1 text-fig.
UozuMI. S. and FUJIE, T., 1966 ; Neogene Molluscan Fauna in Hokkaido. Part II. Description of
the Okushiri fauna associated with Vicary'a, from Okushiri Island, Southwest Hokkaido
Jour. Fac. Sci.. Hokkaido Univ.. Ser. 4, vol. 13, no. 2, 139-163, Pls. 1 1-13, 4 text-figs.
WATANABE. K., ARAI, J. and HAYASHI, T., 1 950 ; Tertiary Geology of the Chichibu Basin (in Japanese). Bull. C.hichibu Mus.. Nat. Hist., no. I , 29-92, Pls. 1-6, 16 text-figs
YABE, H. and HATAl:. K., 1938; On the Japanese Species of Vicarya. Sci. Rep. Tohoku Imp. Univ..
2nd Ser., vol. 21, no. 2, 149-172, Pl. 21.
YAMANA, I., 1 966 ; Neogene Fossil Mollusca from Akenobe, Tottori Prefecture, Japan (in Japanese)
Bull. Japan. Mus. Assoc., no. I , 33-37, Pls. 1-2.
YOKOYAMA, M., 1 923 ; On Some Fossil Mollusca from the Neogene of lzumo. Jap. Jour. Geol Geogr., vol. 2, no. 1, 1-9, Pls. 1, 2.
l08 Katsurm TAKAYASU , 1924; Tertiary Fossils from Kii. Ibid., vol. 2, no. 3, 47-58, Pls. 6, 7
, 1925 ; Molluscan Remams from the Uppermost Part of the Jo-Ban Coal-Field. Jour. Coll
Sci., Imp. Univ. Tokyo, vol. 45, art. 5, 1-34, Pls. 1-6.
, 1926; Fossil Mollusca from Southem Totomi. Jour. Fac. Sci., Imp. Univ. Toky(,. Sec. 2,
･ vol. 1, pt. 9, 377-389, Pls. 44, 45.
, 1929; Neogene Shells from the Province of Chugoku. Ibid., vol. 2, pt. 8, 363-368, P1. 70
YooN, S. and NoDA, H., 1 976 ; A New Species of the Miocene Hwabongri Formation, Ulsan District,
Korea. Sci. Rep., Tohoku Univ,, 2nd Ser., vol. 45, 27-32.
Explanation of Plate I
(All figures in natural size)
iFigs. I a~c. Hermfusus ? mimasakensis (YOKOYAMA)
. ' ' . . _ DQSU coll. cat. no. T1797.
~lg~. '.2, 3. Euspira meisensis (MAKlYAMA)
~ ' ' Flg. 2, DGSU coll. cat. no. T1715; fig. '3, DGSU coll.
Figs. 4, 5 . Neverita (Glossaulax) cf, coticazae (MAKIYAMA)
Fig. 4, DGSU 6011, cat. no. T1798; fig. 4, DGSU coll.
Figs. 6, 7. Tateiwaia tateiwai (MAKIYAMA)
Fig. 6, DGSU coll. cat. no. T1711 ; fig. 7, DGSU coll
Figs. 8, 9. Tateiwaia yamanarii (MAKIYAMA) . Fig. 8, DGSU coll, cat. no. T1799; fig. 9, DGSU coll.
Frg 10. Tristichotrochus_ sp.
' DGSU coll, cat. no. T1800.
cat .
cat.
cat .
cat .
no .
no .
no.
no .
T1713.
T1716.
T1709 .
T1707.
Explanation of Plate II
(All figures in natural size)
Fig.
Figs
Fig.
Figs .
Fi g .
Fig.
Figs .
Fig.
Figs .
Fig.
1 . Vicarya japonica YABE and HATAI
DGSU coll. cat. no. T1704.
2-5b. Anadara (Hataiarca) daitokudoensis (MAKIYAMA)
Fig. 2, Ieft view of core, DGSU coll. cat. no. T1793 ; fig. 3, Ieft view of core, DGSU
coll. cat. no. T1795; fig. 4, right valve, DGSU coll. cat. no. T1729; fig. 5, DGSU
coll. cat. no. T1796, 5a, right view of core, 5b, anterior view of core.
6. Acila (Acila) submirabilis MAKIYAMA
Right valve, DGSU coll. cat. no. T1733
7aHc . Striarca uetsukiensis (HATAI and NISIYAMA)
7a, right valve, 7b, interior view, 7c, dorsal view, DGSU coll. cat. no. T1972
8. Latona sp.
Right valve, DGSU coll. cat, no. T1790
9. "Vasticardium" ogurai (OTUKA)
Left view of core, DGSU coll. cat. no. T1729.
1 Oa~ . Cardilia toyamaensis TSUDA
l Oa, right view of core, I Ob, posterior view of core, I Oc, dorsal view of core, DGSU
coll. cat. no. T1791.
11. "Fabulina" sp.
Right valve, DGSU coll. cat. no. T1789.
1 2a-14. Macoma (Macoma) izurensis (YOKOYAMA) Fig. 12, DGSU coll. cat. no. T1788, 12a, right valve, 12b, dorsal view ; fig. 1 3, Ieft valve,
DGSU coll. cat. no. T1730; fig. 14, Ieft internal mould, DGSU coll. cat. no. T1731
1 5 . Crassostrea gravitesta (YOKOYAMA)
DGSU coll. cat. no. T1734.
Plate II
_ ;sf:~#S~',~ ' * *'.'.'***
S ~""_';;:/~'~;:t~~~#~' ~;
7c
K TAKAYASU Fossil Molluscs from Masuda
籔
6
ba7
b
．a磁
、
8蟻
C01 a
轟、
欝、
9
a
2
干 ・1－1
11
51
4
1
b2131
Explanatlon of Plate 111
(All figures in natural size)
Figs .
Fig.
Figs.
Figs .
1 a-b, 3-8b. Cyclina ? hwabongriensis YOON and NoDA
Fig. 1, DGSU coll. cat. no. T1786, Ia, Ieft valve, Ib, dorsal view ; fig. 3, right valve,
DGSU coll. cat. no. T1783; fig. 4, Ieft valve, DGSU coll. cat. no. T1719; fig. 5,
right view of core, DGSU coll. cat. no. T1782; fig. 6, right valve coated with mud
DGSU coll. cat. no. T1718; fig. 7, right valve, DGSU coll. cat. no. T1784; fig. 8,
DGSU coll. cat. no. T1785, 8a, right valve, 8b, dorsal view.
2. Cyclina takayamai OYAMA Left valve, DGSU coll. cat. no. T1787.
9a-b. Anisocorbula osawanoensis TSUDA
9a, Ieft valve, dorsal view, DGSU coll. cat. no. T1725.
1 O, 1 1 . Cultellus izumoensis (YOKOYAMA)
Fig. 10, Ieft interior view of core, DGSU coll. cat. no. T1732; fig. I l, a part of left
valve, DGSU coll, cat. no. T1781.
